Proteins modified by post-translational addition of fatty acid have been associated with both cellular oncogenic transformation and differentiation. In an effort to gain further knowledge about what roles these modified proteins play, two-dimensional gel electrophoresis patterns of 3H myristylated proteins have been obtained from HL60 cells after experiments were performed with untreated cells, with cells blocked from proliferation, or with cells differentiated to either granulocytes or macrophages. Changes were noted when proliferation was halted, indicating that myristylated proteins are involved in the cell cycle, and when differentiation occurred. Most variations observed were manifested as partial or total decreases in spot intensities on gel autoradiograms when compared to those of untreated cells.